Laminate and manufacturing method of laminate

Abstract

To provide a laminate capable of maintaining durability, while maintaining writing performance or printing performance.SOLUTION: A laminate includes: a fiber substrate; a first protective layer disposed on each of a front face and a rear face of the fiber substrate; and a second protective layer composed of a material absorbing ultraviolet light at least on one face of the fiber substrate. The first protective layer is composed of a material having higher gas barrier properties than those of the second protective layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a laminate and a method for manufacturing the laminate. [Background technology]

[0002] In order to curb global warming and reduce the negative impact on the ecosystem, there is a growing demand for non-plastic materials, and there is a growing demand for materials made from natural fibers that are renewable and have a low impact on the ecosystem. Paper is a typical example of such natural fiber materials and is used for a wide range of purposes.

[0003] However, compared to plastic materials, paper made from such natural fibers often faces problems with deterioration and durability. For example, problems such as discoloration and deterioration, or wavy due to moisture absorption can limit its uses. Paper made from plant fibers in particular faces the unique issue of lignin, a substance that makes up the fiber, reacting with oxygen when exposed to ultraviolet energy, causing discoloration. For this reason, various technologies are being considered to protect paper.

[0004] Known methods for protecting such paper include laminating it with a transparent film that can block ultraviolet rays to prevent fading, and coating the paper with aluminum or resin that has water vapor barrier properties in addition to blocking ultraviolet rays to prevent moisture absorption.

[0005] Patent Document 1 discloses a technology for providing paper with both UV-blocking and gas barrier properties by providing the surface of the paper with a UV-blocking layer containing a resin and an inorganic compound, a metal oxide, that absorbs UV rays. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-94130 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the laminate described in Patent Document 1, a resin layer is formed on a paper base material, which is thought to reduce the original functions of paper, such as making it difficult to write on with a writing instrument or to print on.

[0008] The present invention has been made in consideration of the above problems, and has an object to provide a laminate that can maintain durability while maintaining writing performance and printing performance. [Means for solving the problem]

[0009] The laminate for achieving the above-mentioned object comprises a fiber base material, a first protective layer provided on both the front and back surfaces of the fiber base material, and a second protective layer made of a material that absorbs ultraviolet rays on at least one surface of the fiber base material, and is characterized in that the first protective layer is made of a material that has higher gas barrier properties than the second protective layer. [Effects of the Invention]

[0010] By providing the laminate in this manner, it is possible to provide a laminate that can maintain durability while maintaining writing performance and printing performance. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. [Figure 2] FIG. [Figure 3] FIG. 10 is a diagram showing the analysis results of a laminate. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0013] 1 is a cross-sectional view of a laminate according to this embodiment. The front and back surfaces of a fiber substrate 101 are covered with a gas barrier layer 103 (first protective layer), and at least one surface, which is the surface on which writing or printing is performed, has an ultraviolet-cutting layer 102 (second protective layer) between the gas barrier layer 103 and the fiber substrate 101 to prevent ultraviolet light from passing through the fiber substrate 101.

[0014] 1, the ultraviolet ray blocking layer 102 is provided only on the surface, but the ultraviolet ray blocking layer 102 may be provided over the entire region. That is, the ultraviolet ray blocking layer 102 may be provided over the entire region between the fiber substrate 101 and the gas barrier layer 103.

[0015] 2, an ultraviolet-cutting layer 102 and a gas barrier layer 103 may be provided so as to cover the surface of the fibers 104 exposed on the surface of the fiber substrate 101. In this case, as in the example of FIG. 1, the ultraviolet-cutting layer 102 is provided between the fibers 104 and the gas barrier layer 103 on at least one side of the fibers 104, which is the surface on which writing or printing is performed.

[0016] 1 and 2, when composition analysis is performed perpendicular to the thickness direction from the plane of the paper, two layers, the ultraviolet protection layer 102 and the gas barrier layer 103, are detected on one side before the fiber substrate 101 is detected.Then, on the other side, the laminate is provided so that at least the gas barrier layer 103 is detected.

[0017] By providing the gas barrier layer 103 on both the front and back surfaces of the laminate in this way, it is possible to prevent water vapor and the like from penetrating into the fiber base material 101, causing the fiber base material 101 to absorb moisture and become wavy. In addition, by providing an ultraviolet-cutting layer 102 between the fiber base material 101 and the gas barrier layer 103 on the surface on which writing or printing is performed (at least one surface), it is possible to prevent discoloration of the fiber base material 101 due to the effects of ultraviolet rays.

[0018] 1 and 2, the surface on which writing or printing is performed is described using an example in which the ultraviolet-cutting layer 102 is provided between the fiber substrate 101 and the gas barrier layer 103, but the order of lamination of the ultraviolet-cutting layer and the gas barrier layer may be reversed. That is, the ultraviolet-cutting layer 102 may be the first layer on the fiber substrate 101 (surface of the fibers 104) and the gas barrier layer 103 may be the second layer, or the gas barrier layer 103 may be the first layer and the ultraviolet-cutting layer 102 may be the second layer. Furthermore, if there are three or more layers, the order is not limited to this.

[0019] <Fiber base material> Materials that can be used as the fiber substrate 101 will be described. The fiber substrate 101 can be made of natural fibers, and is not particularly limited to paper, and the raw material can be either plant fibers or animal fibers. Plant fibers that are primarily composed of cellulose, such as wood, cotton, or hemp, can be used, and animal fibers that can be used are raw silk or wool.

[0020] When a paper substrate is used as the fiber substrate 101, it may be paper or paperboard. Examples of paper include newspaper rolls, printing and communication paper, packaging paper, sanitary paper, and miscellaneous paper. Examples of paperboard include cardboard, paperboard for paper containers, building material base paper, paper tube base paper, and paperboard wrapping paper. The fiber substrate may also be partially printed or have writing on it with a writing implement. Examples include printed paper, cardboard, and paintings. Deterioration due to ultraviolet rays and oxidation is not limited to fiber substrates; it can also occur in paints and pigments. In other words, a UV-blocking layer 102 or a gas barrier layer 103 may be laminated on a substrate that has absorbed the ultraviolet rays or retained the paint or pigment.

[0021] <UV-cutting layer (second protective layer)> The UV-cutting layer 102 may be made of any inorganic compound, including, but not limited to, oxides, nitrides, sulfides, nitrides, and carbides. However, it is preferable that the UV-cutting layer 102 is transparent to the visible light region and has UV-cutting properties in the ultraviolet region. Therefore, it is preferable that the material has a band gap of more than 2.5 eV and not more than 4.4 eV, and from the viewpoint of aesthetics, it is more preferable that the band gap is 3.1 eV or more and not more than 4.4 eV.

[0022] The reason why UV blocking ability can be defined by band gap is because the light absorption of a material depends on the material's band gap, and when light with a wavelength that has energy above the band gap enters a material, the light is absorbed without being transmitted. The relationship between this energy E and light is expressed by the following equation (1). E=hν=hc / λ Equation (1) (h: Planck's constant, ν: frequency, c: speed of light, λ: wavelength)

[0023] In other words, the wavelength at which absorption begins can be determined by substituting the band gap energy for E from the relationship λ = 1240 / E. For example, when the band gap is 2.5 eV, light with a wavelength of approximately 500 nm or less is absorbed, and when the band gap is 4.4 eV, light with a wavelength of approximately 280 nm or less is absorbed.

[0024] Generally, the wavelength of light that can be recognized by the human eye is about 400nm to 750nm, so if a material has transparency at least around 500nm, it can be recognized by the human eye, and therefore it is said to be "transparent in the visible light range."

[0025] Furthermore, light known as ultraviolet rays generally has a wavelength of 400nm or less, but the majority of the ultraviolet rays contained in sunlight that reach the earth's surface are between 280nm and 400nm, as the short wavelength ultraviolet rays are absorbed by the ozone layer. Therefore, the ability to absorb wavelengths in this range of 280nm to 400nm is said to be "UV-blocking."

[0026] That is, the ultraviolet ray cutting layer, which has optical transparency in the visible region and ultraviolet ray cutting properties, is preferably made of a material having a band gap of 2.5 eV or more and 4.4 eV or less.

[0027] Examples of materials with a band gap of 2.5 eV or more and 4.4 eV or less include zinc oxide, zinc sulfide, silicon carbide, titanium oxide, gallium nitride, and gallium sulfide, but are not limited to these as long as the band gap is within this range.

[0028] The appropriate thickness of the UV-cutting layer 102 varies depending on the band gap and other optical properties of the material used, as well as the expected UV absorption rate, which varies depending on the application, but if the layer is too thin, sufficient absorption rate cannot be obtained, so it is recommended that the layer be at least 30 nm thick.If the layer is too thick, peeling will occur due to stress in the layer, so the layer should preferably be 500 nm thick or less.

[0029] <Gas barrier layer (first protective layer)> The gas barrier layer 103 may be made of an inorganic compound, and in this embodiment, a layer having a higher gas barrier property than at least the ultraviolet protection layer 102 is used as the gas barrier layer 103. In other words, it is not necessary for the gas barrier layer 103 to have a specific oxygen permeability or water vapor permeability, but it is preferable for the layer to be made of alumina oxide, silicon oxide, or magnesium oxide, which are generally known materials having gas barrier properties. The standard for gas barrier properties is, for example, a coating on a PET film, and the layer is heated to 30 cm under conditions of 20°C and 65% RH. 3 / m 2 ·day·atm or less, and more preferably 10cm 3 / m 2 ·day·atm or less is preferable.

[0030] The gas barrier layer 103 does not need to have UV blocking properties, so there is no upper limit to the band gap required, but it does need to be transparent to the visible light range, so a material with a band gap of 2.5 eV or more is preferable. From the viewpoint of aesthetics, a material with a band gap of 3.1 eV or more is also preferable.

[0031] The appropriate thickness of the gas barrier layer 103 varies depending on the gas barrier properties of the material used and the expected level of gas barrier properties, but a thickness of at least 5 nm is sufficient to achieve gas barrier properties, so a thickness of 5 nm or more is recommended. However, if the thickness is too thick, peeling may occur due to stress in the film, so a thickness of 500 nm or less is preferred.

[0032] The reason why the UV-cutting layer 102 and the gas barrier layer 103 are preferably composed of inorganic compounds is that recyclability is required for fiber substrates, especially paper, from the perspective of environmental protection. Currently, most fiber substrates are coated with organic resins or the like. While using organic resins can be expected to be effective in preventing deterioration to a certain extent, using resins makes separation difficult, reduces the recycling rate, and in some cases makes them unrecyclable. Furthermore, even if they are discarded, they are bad for the environment because they contain organic resin components, and their poor biodegradability could have a negative impact on the ecosystem. For these reasons, inorganic compounds are preferred as materials for the laminate to be laminated to the fiber substrate.

[0033] <Method of manufacturing laminate> The UV-cut layer 102 and the gas barrier layer 103 can be laminated on the fiber substrate 101 to form a laminate, using methods such as chemical vapor deposition (CVD) and physical vapor deposition (PVD). Examples of CVD methods include plasma CVD, which uses plasma, and thermal CVD, which uses heat. Examples of PVD methods include vacuum deposition, ion-assisted deposition, ion plating, and sputtering.

[0034] Atomic layer deposition (ALD) is a more suitable layer formation method. The ALD method, as disclosed in, for example, Patent Document 2009-525406, involves alternately introducing and exhausting two or more source gases, causing reactions between the source gases adsorbed on the target surface, resulting in the formation of thin films atomically. Using aluminum oxide as an example, the process is detailed as follows: (1) aluminum-containing source gas (trimethylaluminum ((CH3)3Al)) and inert argon gas are introduced; (2) the source gas is purged; (3) oxygen-containing source gas (HO + O2) is introduced; and (4) the source gas is purged again. This cycle (1) through (4) is called one cycle, and by repeating this cycle, thin films can be formed atomic layer by atomic layer. The deposition rate per cycle varies depending on the conditions and material, but the reproducibility is high under the same conditions. Therefore, the desired film thickness can be achieved by multiplying the film thickness formed in one cycle by the number of cycles.

[0035] The ALD method has the disadvantage of being slow in deposition speed because it uses the self-regulation of atoms on the surface of the target to build up thin films in atomic layer units. However, when the surface of a fibrous substrate has irregularities due to the fibers, it is possible to form a layer that envelops the irregularities on the surface and even each individual fiber. In other words, the ALD method is preferable for forming a layered structure like the one shown in Figure 2.

[0036] <Evaluation of Examples and Comparative Examples> Next, Table 1 shows the configurations of examples and comparative examples of the laminate according to this embodiment. Note that these configurations are merely examples, and the present invention is not limited to these, and the configuration, film thickness, and film formation method can be changed as appropriate. Each example and each comparative example was evaluated in terms of band gap, gas barrier property, and writability. However, the band gap and gas barrier property were evaluated for a single layer in order to accurately evaluate the performance of the film, and the writability was evaluated for the configuration of each example and comparative example.

[0037] [Table 1]

[0038] (Band gap evaluation) The band gap can be calculated using a Tauc plot after measuring transmittance and reflectance using, for example, a spectrophotometer. In this study, the UV blocking ability of the laminate was evaluated as follows: if the band gap of the single layer of the material used as the UV blocking layer in the laminate was greater than 2.5 eV and less than 4.4 eV, it was evaluated as ◯; otherwise, it was evaluated as ×.

[0039] (Gas barrier evaluation) To evaluate the gas barrier properties, oxygen permeability was measured using an oxygen permeability measuring device (OX-TRAN2 / 22, manufactured by MOCON). The measurement conditions were 20°C and 65% RH. Furthermore, when evaluating the gas barrier properties using a laminate containing a fiber substrate, as in each of the Examples and Comparative Examples, the evaluation is affected by the shape and basis weight of the fiber, resulting in variations in the evaluation. Therefore, a single layer of the material used in each of the Examples and Comparative Examples was formed on a PET film, and the gas barrier properties were evaluated equally. Furthermore, in this embodiment, the gas barrier properties are not evaluated numerically, but are evaluated according to the following criteria. The oxygen gas barrier properties of the single layer are evaluated at 30cm 3 / m 2 If it is larger than 10cm, please use ×. 3 / m 2 ·Day·30cm larger than ATM 3 / m 2 ·day·atm or less is △. 10cm 3 / m 2 ·day·atm or less was defined as 〇 and evaluated.

[0040] (Written evaluation) The writability was evaluated by writing on the surface of the laminate of each example and each comparative example with a B pencil. If the writing feel was as good as that of uncoated high-quality paper, it was rated as ◯; if the tip of the pencil was a little slippery and the writing feel was poor, it was rated as △; and if writing was impossible, it was rated as ×.

[0041] The results of evaluating the band gap and gas barrier properties of a single layer are shown in Tables 2 and 3. The zinc oxide and titanium oxide selected for the UV-cut layer this time were confirmed to have a band gap in the range of more than 2.5 eV and less than 4.4 eV. The aluminum oxide and magnesium oxide selected for the gas barrier layer each had a gas barrier property of 10 cm 3 / m 2 ·day·atm or less.

[0042] [Table 2]

[0043] [Table 3]

[0044] Example 1 The fiber base material was fine paper (OK Prince Fine Paper, manufactured by Oji Co., Ltd., basis weight: 81.4 g / m 2 ) was used to form a laminate on the surface of the fiber substrate 101 by atomic layer deposition (ALD). When forming the film, the substrate, paper, was attached to a substrate holder in the film formation chamber and fixed in place. When forming a film on the opposite side, the substrate was flipped over and fixed in place. The materials used were zinc oxide for the UV-blocking layer and aluminum oxide for the gas barrier layer. The film formation rates for each material by atomic layer deposition in this study were 1.8 Å / cycle for zinc oxide and 1.0 Å / cycle for aluminum oxide. Therefore, film formation was performed by repeating the cycle for each layer until the target film thickness shown in Table 1 was achieved. In the following examples and comparative examples, the film formation rate for each cycle was similarly calculated, and film formation was repeated until the desired film thickness was achieved to obtain a laminate.

[0045] <Example 2> The fiber base material was fine paper (OK Prince Fine Paper, manufactured by Oji Co., Ltd., basis weight: 81.4 g / m 2) was used to form a laminate by atomic layer deposition (ALD). In Example 2, the fixing method was different from that in Example 1, and films were formed on both sides simultaneously as a fixing method that allowed gas to easily diffuse to both sides of the paper. In other words, when forming layers, layers with exactly the same configuration were formed on both sides. The materials selected for use were zinc oxide for the UV-cutting layer and magnesium oxide for the gas barrier layer. Furthermore, because magnesium oxide has deliquescence, the gas barrier layer was used as the first layer and the UV-cutting layer was laminated on top of it.

[0046] Example 3 The fiber base material was fine paper (OK Prince Fine Paper, manufactured by Oji Co., Ltd., basis weight: 81.4 g / m 2 ) was used to form a laminate by atomic layer deposition (ALD). Titanium oxide was selected as the material for the ultraviolet protection layer, and aluminum oxide was selected as the material for the gas barrier layer. The film formation method was the same as in Example 1.

[0047] Example 4 Kraft paper (G Olympus, manufactured by Nippon Paper Industries Co., Ltd., basis weight: 85 g / m) was used as the fiber base material. 2 ) was used to form a laminate by atomic layer deposition (ALD). The materials used were zinc oxide for the ultraviolet protection layer and aluminum oxide for the gas barrier layer. The film formation method was the same as in Example 1.

[0048] <Example 5> Using cardboard (K5·A flute) as the fiber substrate, a laminate was formed by atomic layer deposition (ALD). The materials used were zinc oxide for the UV-cut layer and aluminum oxide for the gas barrier layer. The film formation method was the same as in Example 1.

[0049] <Comparative Example 1> Using high-quality paper as the fiber substrate, a laminate was formed by atomic layer deposition (ALD). As shown in Table 1, a single layer of zinc oxide, which was used in Example 1 as an ultraviolet-cutting layer, was formed on the substrate surface. The film formation method was the same as in Example 2.

[0050] <Comparative Example 2> A laminate was formed by atomic layer deposition using high-quality paper as the fiber substrate. As shown in Table 1, a gas barrier layer was formed on the surface of the substrate as a single layer of aluminum oxide, which was used in Example 1. The film formation method was the same as in Example 2.

[0051] <Comparative Example 3> Using high-quality paper as the fiber substrate, a laminate was formed using a bar coater. The coating material was polyvinylidene chloride emulsion (PVDC) (Diofan B204, manufactured by Solvay), which is known to have high gas barrier properties. The coating amount was adjusted so that the film thickness after drying would be 1 to 2 μm.

[0052] Table 4 summarizes the results of each example and comparative example. Examples 1-5 and comparative examples 1-2 had good writability. This is thought to be because the film thickness was thin and unevenness due to the surface fibers remained, resulting in high writability. On the other hand, the resin of comparative example 3 was confirmed to be somewhat slippery. It was also confirmed that laminates could be formed without problems using not only fine paper but also kraft paper and cardboard as the fiber substrate.

[0053] [Table 4]

[0054] Furthermore, in Examples 1 to 5, high adhesion was confirmed between the fiber substrate 101 and the layer formed on its surface. This is thought to be because the laminate contained a small amount of hydrocarbon bonds due to the film formation using the ALD method, which increased adhesion to cellulose, a carbohydrate. Therefore, thermal desorption spectroscopy (TDS) was performed on the aluminum oxide used in Example 1. Using a thermal desorption spectroscopy (EMD-WA1000S / W manufactured by Electronic Science Co., Ltd.), the aluminum oxide was heated from room temperature to 450°C, and mass analysis was performed on the generated gas. The spectrum of heated quartz as a reference and the results for the aluminum oxide used in Example 1 are shown in Figure 3. Compared to the quartz used for comparison, a large amount of CH3 component (m / z = 15) was observed to be desorbed.

[0055] That is, by using plant fibers containing cellulose as the main component as the fiber base material 101 and forming a film on the surface thereof using the ALD method, it is possible to provide a laminate with higher adhesiveness.

[0056] <Summary of the embodiment> The disclosure of the present specification includes at least the following configurations.

[0057] (Item 1) A fiber substrate; a first protective layer provided on both the front and back surfaces of the fiber substrate; a second protective layer made of an ultraviolet absorbing material on at least one surface of the fiber base material; The laminate is characterized in that the first protective layer is made of a material having higher gas barrier properties than the second protective layer.

[0058] (Item 2) Item 2. The laminate according to item 1, wherein the material of the second protective layer has a band gap of 2.5 eV or more and 4.4 eV or less.

[0059] (Item 3) 3. The laminate according to item 1 or 2, wherein the fiber substrate is a substrate containing cellulose as a main component.

[0060] (Item 4) 2. The laminate according to item 1, wherein the first protective layer and the second protective layer contain an inorganic metal compound.

[0061] (Item 5) 5. The laminate according to item 4, wherein the inorganic metal compound contains at least one of zinc oxide, zinc sulfide, silicon carbide, titanium oxide, gallium nitride, and gallium sulfide.

[0062] (Item 6) 6. The laminate according to any one of items 1 to 5, wherein the thickness of the first protective layer is 5 nm or more and 500 nm or less.

[0063] (Item 7) 7. The laminate according to any one of items 1 to 6, wherein the second protective layer has a thickness of 30 nm or more and 500 nm or less.

[0064] (Item 8) 8. The laminate according to any one of items 1 to 7, wherein the second protective layer is provided between the fiber substrate and the first protective layer.

[0065] (Item 9) forming a second protective layer made of an ultraviolet absorbing material on at least one surface of the fiber substrate; and forming a first protective layer having a higher gas barrier property than the second protective layer on the front and back surfaces of the fiber substrate.

[0066] (Item 10) The fiber substrate is a substrate containing cellulose as a main component, 10. The manufacturing method according to item 9, wherein the step of forming the second protective layer or the step of forming the first protective layer is performed using an atomic layer deposition method.

Claims

1. A fiber substrate; a first protective layer provided on both the front and back surfaces of the fiber substrate; a second protective layer made of an ultraviolet absorbing material on at least one surface of the fiber base material; The laminate, wherein the first protective layer is made of a material having higher gas barrier properties than the second protective layer.

2. 2. The stack according to claim 1, wherein the material of the second protective layer has a band gap of 2.5 eV or more and 4.4 eV or less.

3. 2. The laminate according to claim 1, wherein the fibrous substrate is a substrate containing cellulose as a main component.

4. The laminate according to claim 1 , wherein the first protective layer and the second protective layer contain an inorganic metal compound.

5. 5. The laminate according to claim 4, wherein the inorganic metal compound contains at least one of zinc oxide, zinc sulfide, silicon carbide, titanium oxide, gallium nitride, and gallium sulfide.

6. 2. The laminate according to claim 1, wherein the first protective layer has a thickness of 5 nm to 500 nm.

7. 2. The laminate according to claim 1, wherein the second protective layer has a thickness of 30 nm to 500 nm.

8. The laminate according to claim 1 , wherein the second protective layer is provided between the fiber base material and the first protective layer.

9. forming a second protective layer made of an ultraviolet absorbing material on at least one surface of the fiber substrate; and forming a first protective layer having a higher gas barrier property than the second protective layer on the front and back surfaces of the fiber substrate.

10. The fiber substrate is a substrate containing cellulose as a main component, The manufacturing method according to claim 9 , wherein the step of forming the second protective layer or the step of forming the first protective layer is performed by using atomic layer deposition.

Images